Subterranean fluids and methods of using these fluids in subterranean formations

Abstract

Subterranean fluids comprising a hydraulic cement in an invert emulsion, and methods of using such fluids in subterranean well cementing operations, are provided. The fluids comprise a hydraulic cement and an invert emulsion of oil, water, and a surfactant. Optionally, other ingredients may be included in the fluids.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional patent application of commonly-owned U.S. patent application Ser. No. 10 / 639,702, filed Aug. 12, 2003, entitled “Subterranean Fluids and Methods of Using These Fluids in Subterranean Formations,” by Lance E. Brothers, which is incorporated by reference herein for all purposes.BACKGROUND OF THE INVENTION [0002] The present invention relates to subterranean fluids, and more particularly, to subterranean fluids comprising a hydraulic cement in an invert emulsion, and methods of using such fluids in subterranean operations. [0003] During the drilling of a well bore in a subterranean formation, a drilling fluid may be circulated through a drill pipe and drill bit into the well bore, and subsequently flow upward through the well bore to the surface. The drilling fluid functions, inter alia, to cool the drill bit, lubricate the rotating drill pipe to prevent it from sticking to the walls of the well bore, preve...

AI Technical Summary

Benefits of technology

The present invention is about using a special fluid in subterranean wells to cement them. This fluid contains a type of cement and a special kind of oil, water, and chemical called a surfactant. The use of this fluid helps to improve the quality and stability of the cement used in the well. The technical effect of this invention is to provide a better and more reliable method for cementing subterranean wells.

Problems solved by technology

During that time, the drilling fluid may progressively increase in gel strength whereby portions of the drilling fluid in the well bore may become increasingly difficult to displace.

However, if the drilling fluid has developed sufficient gel strength during its residence within the well bore, an operator may be unable to displace all of the drilling fluid with the cement composition.

This is problematic because the drilling fluid is generally not settable; therefore, formation fluids may enter and flow along the well bore, which is highly undesirable.

However, these methods have not met with success, as conventional settable spotting fluids include blast furnace slag and other hydraulic components which may begin to set at relatively low temperatures, e.g., temperatures less than about 90° F. Also, certain slag-containing settable spotting fluids may be intolerant to cement composition contamination, causing the settable spotting fluids to cement prematurely upon contact with well cement.

Conventional settable spotting fluids may also demonstrate other problems, including but not limited to undesirable instability as well as a general inability to develop significant compressive strength upon setting.

For example, the invert emulsions found in most conventional settable spotting fluids typically become unstable within about one week after their formulation.

This is problematic because it often necessitates formulating the invert emulsion shortly before placing the spotting fluid in a subterranean formation.

If an excessive amount of the invert emulsion is formed, it generally cannot be re-used and is often disposed of, which disposal may further increase the cost of a particular job.

Furthermore, the general inability of most conventional settable spotting fluids to develop significant compressive strength upon setting is also problematic, because, inter alia, where formation fluids are present under a pressure sufficient to overcome the settable spotting fluid's low compressive strength, such formation fluids may continue to enter and flow along the well bore, which is undesirable and defeats the major purpose of using settable spotting fluids—to provide zonal isolation.